Downhole jet pump

ABSTRACT

A wellsite pumping system, comprising a gas processing system including a source of compressed gas, the source of compressed gas having a low pressure inlet and a high pressure outlet, coil tubing connected to the high pressure outlet of the gas processing system, the coil tubing including a first tubing string connected to the high pressure outlet and a second tubing string running parallel to the first tubing string and having an opening for entry of fluid at a remote end from the high pressure outlet; and a venturi connecting the second tubing string to the first tubing string such that, in operation, passage of gas through the venturi from the first tubing string draws production fluid into the second tubing string. Preferably, the second tubing string is suspended within the first tubing string. The venturi may be formed by a horizontal passageway communicating with a vertical passageway with a restriction.

BACKGROUND OF THE INVENTION

[0001] This invention relates to equipment used for producing wells.

[0002] Oil and gas wells have been produced by a jet pump in which innerand outer strings of tubing are connected downhole using a venturi, andliquid flow through the outer tubing string then through the venturiinto the inner tubing string draws production fluid into the innertubing through an opening into the inner tubing. This process has beenfound to work, but requires a suitable liquid.

[0003] Cleaning out wells conventionally with a coiled tubing unit isaccomplished by forcing compressed air/gas down the coiled tubing to thebottom of the well and returning the fluid/fill up the annulus betweenthe coiled tubing and the wells original production casing. The fluidsare carried up the annulus in slugs causing a pressure build-up in thelower portion of the well. This pressure build up may force fluids,fill, and air back into the producing zone, which may cause formationdamage. Wells with production casing larger than four and one half inchare difficult to clean out due to reduced annular velocity of thecompressed air. To clean a well out in this manner, the casing gas isvented to atmosphere through the entire job. This is expensive and notenvironmentally friendly. This invention is directed to providing animproved pumping system.

SUMMARY OF THE INVENTION

[0004] There is therefore provided in accordance with the invention awellsite pumping system, comprising a gas processing system including asource of compressed gas, the source of compressed gas having a lowpressure inlet and a high pressure outlet, coil tubing connected to thehigh pressure outlet of the gas processing system, the coil tubingincluding a first tubing string connected to the high pressure outletand a second tubing string running parallel to the first tubing stringand having an opening for entry of fluid at a remote end from the highpressure outlet; and a venturi connecting the second tubing string tothe first tubing string such that, in operation, passage of gas throughthe venturi from the first tubing string draws production fluid into thesecond tubing string. Preferably, the second tubing string is suspendedwithin the first tubing string. The venturi may be formed by ahorizontal passageway communicating with a vertical passageway with arestriction.

[0005] In one aspect of the invention, the source of compressed gasforms part of a wellsite inert gas injector. The inert gas injectorcomprises an internal combustion engine, a gas processing systemconnected to receive low pressure exhaust gas from the internalcombustion engine, a pump within the gas processing system, the pumphaving a low pressure inlet for receiving exhaust gases and the pumphaving a high pressure outlet; and coil tubing connected to the highpressure outlet of the gas processing system. The gas processing systempreferably comprises one or more of a particulate filter, exhaust coolerand exhaust separator in series, and in that order before the pump. Thepump may be a compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] There will now be described preferred embodiments of theinvention with reference to the drawings by way of illustration, andwithout intending to limit the generality of the claims, in which:

[0007]FIG. 1 is a schematic showing an embodiment of a source ofcompressed gas for use with an embodiment of the invention; and

[0008]FIG. 2 is a schematic showing a down hole jet pump for use with anembodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0009] In this patent document, “comprising” is used in its inclusivesense, and does not exclude other elements being present in theinvention to which a claim refers. Use of the indefinite article “a”before an element of a claim means that at least one of the elements ispresent.

[0010] A wellsite inert gas injector 10 is preferably truck mounted asshown in the figure and utilizes exhaust from the truck's internalcombustion engine 12 as source of inert gas. Preferably, the engine is adiesel engine. The exhaust is provided to coil tubing 14, which ismounted on the truck deck 16 in conventional manner. A conventionalconnection (not shown) is used to connect the outlet 18 to the coiltubing 14. Between the engine 12 and coil tubing 18 is a gas processingsystem 20 that is connected to receive low pressure exhaust gas from theinternal combustion engine and provide high pressure inert gas to thecoil tubing 14 through outlet 18. Low pressure and high pressure arerelative terms. What matters is that gas at the high pressure outlet 18has sufficient pressure for use down a well.

[0011] The gas processing system 20 incorporates several modules toprocess the gas to make it suitable for downhole use. The modules areconnected in series by conventional gas tight couplings. First, on theexhaust outlet of the engine 12, is a catalytic diesel particulatefilter 22, which may be one manufactured by Nett Technologies Inc.Details of the Nett diesel filter are available from Nett, and brieflydescribed in the following. The Nett diesel filter 22 utilizescordierite wall-flow monoliths to trap the soot produced by heavy-dutydiesel engines. A cylindrical filter element in the filter 22 has ofmany square parallel channels running in the axial direction, separatedby thin porous walls. The channels are open at one end, but plugged atthe other. Particulate laden exhaust gases are forced to flow throughthe porous walls. Gas is able to escape through the pores in the wallmaterial. Particulates, however, are too large to escape and are trappedin the filter walls. A proprietary noble metal catalyst is coated ontothe inside surface of the filter monolith. The catalyst lowers the sootcombustion temperature to allow the filter to regenerate. Theaccumulated soot is oxidized in the filter during regular operation ofthe engine. Periods with exhaust temperatures of at least 350-400degrees Fahrenheit are necessary for proper filter regeneration.However, so far as this invention is concerned in its broadest preferredaspect, a particulate filter is required to sufficiently clean theexhaust that the gas processing components are not damaged and theremaining particulate in the inert gas does not have a negative effecton the well.

[0012] Following the filter 22 is an exhaust cooler 24, for example afin type fan driven cooler, or other suitable cooler to reduce thetemperature of the gases to a temperature suitable for compression, asfor example cooling the exhaust gases from about 500 degrees to 90degrees Fahrenheit. Following the cooler 24 is a conventional liquid/gasseparator 26 for removing any liquid droplets that condense out of theexhaust when it is cooled. It may be either free standing or built intothe exhaust cooler. Following the separator 26 is a compressor 28 orother suitable pump with a low pressure inlet 30 and a high pressureoutlet 18. The compressor 28 should compress the exhaust gas to asufficient pressure for cleaning a well, or such other application thatthe invention might be used for.

[0013] The inert gas generator so described is mobile and may be takenfrom well site to well site. At the well site, the engine suppliesnitrogen rich, essentially oxygen free, but contaminated inert gas foruse in well clean out operations. The gas process cleans the gas for usedownhole.

[0014] With an efficient internal combustion engine, it is expected thatthe resulting exhaust will be essentially oxygen free, with anyremaining free oxygen captured by carbon monoxide to form carbondioxide. Incorporation of other inert gases from the atmosphere besidesnitrogen is acceptable. The water separator should separate out waterdroplets to avoid damage to the compressor, but need not render theexhaust stream free of water vapor. The exhaust stream may be 100% watersaturated. The maximum preferred inlet temperature to the compressor is10° F. above ambient. A preferred compressor is a Hurricane Compressorcapable of pumping at 330 cubic feet per minute at 2000 psi.

[0015] The coil tubing 14 is formed of two strings of endless tubingrunning in the well simultaneously (one inside the other). FIG. 2 showsthe inner tubing 40 and outer tubing 42 with an annulus 44 between them.The inner tubing 40 extends below the outer tubing 42 and has an opening46 for the flow of downhole fluid, for example production hydrocarbons,into the inner tubing 40. A venturi 48 is provided with an inlet 50communicating with the annulus 44 and an outlet 52 communicating withthe bore of the inner tubing 40. The venturi 48 may be formed by ahorizontal passageway 54 communicating with a vertical passageway 56having a restriction 58 at the outlet 52 where the flow through theventuri enters the inner tubing 40. Exhaust is pumped down the annulus44 between the two strings 40, 42, through the venturi 48 and lifts wellfluids up the inside string 40. Such a system may be used to produce oilwells.

[0016] By using a jet pump, the well need not be vented to atmosphereand would have to be taken off production to be cleaned out. Such jetpumps are known in the art in themselves, but the use of the exhaustsystem described would provide lower installation costs, quicker startup, less harm from sand to the pump and ready variation of productionvolumes from the well. This application is filed simultaneously with anapplication claiming the inert gas generator.

[0017] Immaterial modifications may be made to the invention describedhere without departing from the essence of the invention.

We claim:
 1. A wellsite pumping system, comprising: a gas processing system including a source of compressed gas, the source of compressed gas having a low pressure inlet and a high pressure outlet; coil tubing connected to the high pressure outlet of the gas processing system, the coil tubing including a first tubing string connected to the high pressure outlet and a second tubing string running parallel to the first tubing string and having an opening for entry of fluid at a remote end from the high pressure outlet; and a venturi connecting the second tubing string to the first tubing string such that, in operation, passage of gas through the venturi from the first tubing string draws production fluid into the second tubing string.
 2. The wellsite pumping system of claim 1 further comprising: an internal combustion engine; the gas processing system being connected to receive low pressure exhaust gas from the internal combustion engine; and a pump being provided within the gas processing system, the pump having a low pressure inlet for receiving exhaust gases and the pump having a high pressure outlet.
 3. The wellsite pumping system of claim 2 in which the pump is a compressor and the gas processing system comprises an exhaust cooler.
 4. The wellsite pumping system of claim 2 in which the pump is a compressor and the gas processing system comprises an exhaust separator.
 5. The wellsite pumping system of claim 2 in which the pump is a compressor and the gas processing system comprises a particulate filter.
 6. The wellsite pumping system claim 2 in which the gas processing system comprises a particulate filter, exhaust cooler and exhaust separator in series, followed by a compressor.
 7. The wellsite pumping system of claim 2 in which the pump is a compressor and the gas processing system comprises a particulate filter followed by an exhaust cooler and exhaust separator.
 8. The wellsite pumping system of claim 7 in which the exhaust cooler is followed by the exhaust separator.
 9. The wellsite pumping system of claim 1 in which the first tubing string is disposed within the second tubing string. 